Yarn and fabric having improved abrasion resistance

ABSTRACT

The present invention relates to a yarn having improved abrasion resistance and a fabric made from that yarn, as well as process for preparing the yarn and fabric. The yarn includes (a) aramid fibers and (b) up to 40 weight percent of fibers of synthetic polymers having a melting point between 200 and 300 degrees C., based upon the total weight of (a) and (b) only, the yarn or fabric including the yarn being heat treated at a temperature below the melting point of the fibers of component (b).

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to the field of yarns and fabrics thatthat are abrasion resistant, and in particular it relates to the fieldof yarns and fabrics that include abrasion-resistant or cut-resistantfibers.

[0003] 2. Description of Related Art

[0004] Protective apparel such as gloves that include abrasion-resistantor cut-resistant yarn are known in the art. For example, U.S. Pat. No.5,822,791, discloses a protective glove that is resistant to cuts and tothe penetration of liquid. The glove is made from a cut-resistant yarn,such as yarn made from aramid fibers, an intermediate layer that of anatural fiber, and an outer layer of a flexible, elastomeric materialimpervious to liquid.

[0005] U.S. Pat. No. 6,021,523 discloses a hand covering that is heatand abrasion resistant which is made by using a fabric formed fromaramid fiber that is wound with a top cover of a yarn of oxidizedpolyacrylonitrile or polyacrylate. The aramid fiber is conditioned withsteam and then with an ignition resistant wax or an organosiliconecompound.

[0006] Cut-resistant and abrasion-resistant gloves are typically used inapplications that subject the gloves to repeated exposure to sharpobjects. As a result of this exposure, the gloves have a limited wearlife and need to be replaced often.

[0007] As shown in U.S. Pat. No. 4,920,000, there have been attempts toimprove the abrasion resistance of gloves by blending aramid fibers withother high abrasion-resistant fibers such as nylon. The improvement inabrasion resistance of articles made by such blends of aramid and nylonfibers is proportional to the amount of nylon fibers in the blend, butthe improvement in such articles is still limited.

[0008] Accordingly, there is a need in the art to provide a yarns andfabrics that have improved cut resistance and abrasion resistance so asto extend the wear-life of articles such as gloves that are made fromthose yarns and fabrics.

SUMMARY OF THE INVENTION

[0009] The present invention relates to a yarn having improved abrasionresistance, a fabric that includes that yarn, and a process forpreparing the yarn or fabric. The yarn includes (a) aramid fibers and(b) up to 40 weight percent of fibers of synthetic polymers having amelting point between 200 and 300 degrees C., based upon the totalweight of (a) and (b) only, the yarn having been heat treated at atemperature below the melting point of the fibers of component (b). Theheat treatment of the yarn may take place before or after the yarn ismade into a fabric.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention is directed to a yarn, and fabrics whichinclude that yarn, that have an increased resistance to abrasioncompared to conventional abrasion resistant yarns and fabrics, and yetare not undesirably stiff.

[0011] The yarns of the invention include (a) aramid fibers and (b) upto 40 weight percent of fibers of synthetic polymers having a meltingpoint between 200 and 300 degrees C. An important aspect of theinvention is that the yarns, or fabric that includes the yarns, are heattreated at a temperature below the melting point of the fibers ofcomponent (b).

[0012] The aramid fibers used in component (a) of the yarns or fabric ofthis invention are para-aramid fibers. By para-aramid fibers is meantfibers made from para-aramid polymers or fibers made from what are knownas rigid rod polymers. A preferred polymer is poly(p-phenyleneterephthalamide)(PPD-T). By PPD-T is meant the homopolymer resultingfrom mole-for-mole polymerization of p-phenylene diamine andterephthaloyl chloride and, also, copolymers resulting fromincorporation of small amounts of other diamines with the p-phenylenediamine and of small amounts of other diacid chlorides with theterephthaloyl chloride. As a general rule, other diamines and otherdiacid chlorides can be used in amounts up to as much as about 10 molepercent of the p-phenylene diamine or the terephthaloyl chloride, orslightly higher, provided that the other diamines and diacid chlorideshave no reactive groups which interfere with the polymerizationreaction. The term PPD-T also includes copolymers resulting fromincorporation of other aromatic diamines and other aromatic diacidchlorides such as, for example, 2,6-naphthaloyl chloride or chloro- ordichloroterephthaloyl chloride; provided only that the other aromaticdiamines and aromatic diacid chlorides be present in amounts which donot adversely affect the properties of the para-aramid.

[0013] Additives can be used with the para-aramid in the fibers and ithas been found that up to as much as 10 percent, by weight, of otherpolymeric material can be blended with the aramid or that copolymers canbe used having as much as 10 percent of other diamine substituted forthe diamine of the aramid or as much as 10 percent of other diacidchloride substituted for the diacid chloride of the aramid.

[0014] P-aramid fibers may be made by processes well known in the art,and are generally spun by extrusion of a solution of the p-aramidthrough a capillary into a coagulating bath. In the case ofpoly(p-phenylene terephthalamide), the solvent for the solution isgenerally concentrated sulfuric acid and the extrusion is generallythrough an air gap into a cold, aqueous, coagulating bath.

[0015] The fibers of component (b) of the invention may be fibers ofnylon, polyester, or blends thereof.

[0016] As used herein, the term “nylon” means aliphatic polyamidepolymers including with polyhexamethylene adipamide (nylon 66),polycaprolactam (nylon 6), polybutyrolactam (nylon 4),poly(9-aminononanoic acid) (nylon 9), polyenantholactam (nylon 7),polycapryllactam (nylon 8), polyhexamethylene sebacamide (nylon 6,10),and the like. Polyhexamethylene adipamide (nylon 66) is a preferrednylon.

[0017] “Nylon fibers” means any fibers made from nylon. Nylon fibers aregenerally spun by extrusion of a melt of the nylon polymer through acapillary into a gaseous congealing medium and other processes known inthe art.

[0018] As used herein the term “polyester” means polymers synthesizedfrom the polycondensation of a diol and a dicarboxylic acid.

[0019] “Polyester fibers” means any fibers made from polyester.Polyester fibers are spun from molten polymer by the melt spinningprocess and other processes known in the art.

[0020] The yarn of the invention may include up to about 40 weightpercent of the fibers of component (b). A higher amount of the fibers ofcomponent (b) may be used but no increase in the abrasion resistance ofthe yarn or fabric made using the yarn is observed in doing so. Apreferred range of fibers in the yarn is from about 70 to about 95weight percent of fibers of component (a) and from about 5 to about 30weight percent of fibers of component (b), and a more preferred range isfrom about 75 to about 90 weight percent of fibers of component (a) andfrom about 10 to about 25 weight percent of fibers of component (b).These weight percents are based upon the relative amounts of components(a) and (b) only.

[0021] The fibers of components (a) and (b) are preferably staple fibersof a particular length and of a particular linear density. For use inthis invention, synthetic fiber staple lengths of 2.5 to 15 centimeters(1 to 6 inches) may be used, with lengths of 3.8 to 11.4 centimeters(1.5 to 4.5 inches) being preferred. The linear density of the fibersmay be from 0.5 to 7 decitex, preferably from 1 to 3 decitex.

[0022] The fibers can be spun into yarns using any conventional means,such as ring spinning, air-jet spinning, Murata-jet spinning, orfriction spinning. The yarns, once spun, may be twisted together to makeplied yarns.

[0023] An important aspect of the present invention is that the yarn orfabric is heat treated. This heat treatment may be conducted on yarnwhich is then made into a woven or knitted fabric. This fabric exhibitsan increase in abrasion resistance compared to fabric in which the yarnis not heat treated. Alternatively, the yarn which has not been heattreated may be made into a woven or knitted fabric and then that fabricis heat treated. This fabric also exhibits an increase in abrasionresistance compared to fabric in which the yarn is not heat treated.

[0024] The woven or knitted fabric may include 100 weight percent of theyarns of the invention. Preferably the fabric includes no less that 10weight percent of the yarns of the invention, more preferably no lessthan 40 weight percent of the yarns of the invention.

[0025] The yarn or fabric should be heat treated at a temperature belowthe melting point of component (b). In general, the yarn or fabricshould be heat treated at a temperature of from about 100 to about 300degrees C. for a time of from about 10 to about 20 minutes. A preferredtemperature is from 150 to 300 degrees C., and a more preferredtemperature is from about 200 to about 250 degrees C. Stated anotherway, the yarn or fabric may be heat treated at a temperature less thanabout 90 percent of the melting point of component (b). A preferredheating time is from about 5 to about 10 minutes. The heating istypically carried out at atmospheric pressure.

[0026] Temperatures above 300 degrees C. may be used but such highertemperatures are not practical since above that temperature polyestermelts and the heat-treated yarn or fabric becomes undesirably stiff.

[0027] Similarly, heating times of greater than 20 minutes may be used,but such greater heating times are not practical since such longerheating times can result in the yarn or fabric becoming undesirablystiff.

[0028] The yarn and fabric of the invention may be used in any articlethat is exposed to abrasion and where a high resistance to abrasion isdesired. Examples of such articles include chaps, protective apparel,aprons, sleeves, hand coverings such as gloves, and the like.

EXAMPLES

[0029] The abrasion resistance of various fabrics was tested in thefollowing examples using the test method titled “Standard Method forAbrasion Resistance of Textile Fabrics”, ASTM Standard D3884-92. In thistest, a sample fabric is abraded using rotary rubbing under controlledconditions of pressure and abrasive action. In particular, a TaberAbraser and a #H-18 abrasive wheel was used to abrade fabric samplesunder a load of 500 grams. The abrasion was continued until the abrasivewheel reached the point where it rubbed through of the fabric sample.The number of revolutions to reach the point of rub-through wasdetermined for four samples and the average is reported.

Example 1 and Comparative Example 2

[0030] These Examples compare the effect of heat treatment on certainfabrics. A high abrasion resistant fabric of present invention wasprepared from ring-spun yarns of intimate blends of PPD-T staple fibersand polyester fibers. The PPD-T fibers were 1.5 dpf and 1.5 inches long,and polyester fibers were 1.2 dpf and 1.5 inches long. A picker blendsliver of 90 weight percent PPD-T and 10 weight percent polyester wasprepared and processed by the conventional cotton system into spun yarnhaving 3.2 twist multiplier using a ring spinning frame. The yarn somade was 10 cc (cotton count). Two of these single yarns were then pliedtogether with reverse twist to form a balanced yarn of 10/2 cc.

[0031] The 10/2 cc yarns were knitted into samples of gloves using astandard Sheima Seiki glove knitting machine. The machine knitting timewas adjusted to produce glove bodies about one meter long to providefabric samples for subsequent cut and abrasion testing. The samples weremade by feeding 3 ends of the 10/2 cc yarn to the glove knitting machineto yield fabric samples of about 20 oz/sq. yd (0.67 kg/sq. meter). Thefabric was then heat treated in oven at 250C for 10 minutes.

[0032] For comparative purposes, there was used a sample of the samefabric that was not heat treated.

[0033] The heat treated fabric and the non heat-treated fabric were bothsubjected to the aforementioned ASTM abrasion resistance test and theresults are listed in Table 1 below. TABLE 1 Example No. AbrasionResistance (cycles) Ex. 1 2049 C. Ex. 2 971

[0034] These Examples show the unexpected increase in the abrasionresistance of the fabrics of the invention.

Comparative Example 3 and Examples 4-6

[0035] These Examples show the effect of the heating temperature on theabrasion resistance of fabrics. The fabric made in Example 1, beforeheat treating, was heat treated at 3 different temperatures for the sameamount of time, 10 minutes. The abrasion resistance of the heat treatedfabrics was measured as in Example 1, and the results are listed inTable 2 below. TABLE 2 Example Abrasion Resistance No. Temp. (C.)(cycles) C. Ex. 3 no heat 971 treatment Ex. 4 100 1265 Ex. 5 200 1653Ex. 6 250 2049

[0036] These Examples show the unexpected improvement in abrasionresistance in the fabric that is heat treated in accordance with thepresent invention.

Comparative Example 7 and Examples 8-12

[0037] These Examples show the effect of effect of heating time on theabrasion resistance of a fabric. The fabric made in Example 1, beforeheat treating, was heat treated at 250 degrees C. for 5 different timeperiods. The abrasion resistance of the heat treated fabrics wasmeasured as in Example 1, and the results are listed in Table 3 below.TABLE 3 Example No. Time (min.) Abrasion Resistance (cycles) C. Ex. 7 0900 Ex. 8 5 1600 Ex. 9 10 1800 Ex. 10 15 2000 Ex. 11 20 2300 Ex. 12 301700

[0038] These Examples show the unexpected improvement in abrasionresistance in the fabric that is heat treated in accordance with thepresent invention. The data show that when the fabric was he at treatedfor 30 minutes at 250C, the abrasion resistance was higher than thecomparative Example which had not been heat treated but had decreasedcompared to the fabric of Example 11 that had been heat treated for 20minutes.

[0039] Comparative Example 13 and Examples 14-17

[0040] These Examples show the effect of the amount of component (b) onthe abrasion resistance of a fabric. A high abrasion resistant fabricwas prepared from ring-spun yarns of intimate blends of PPD-T staplefibers and nylon fibers. The PPD-T fibers were 1.5 dpf and 1.5 incheslong, and the nylon fibers were 1.1 dpf and 1.5 inches long.

[0041] A picker blend sliver of PPD-T and nylon was prepared with 4different blends of PPD-T and nylon and processed by the conventionalcotton system into spun yarns having 3.2 twist multiplier using a ringspinning frame. The yarns so made were 10 cc (cotton count). Two ofthese single yarns were then plied together with reverse twist to form abalanced yarn 10/2 cc.

[0042] The fabric samples were made as in Example 1. For comparisonpurposes a fabric was also made in the same way except that the fabricwas made from 100% of the PPD-T fibers

[0043] The fabric samples were then heat treated at 250C for 10 minutes.The abrasion resistance of the heat-treated and non heat-treated fabricsare listed in Table 4 below. TABLE 4 Abrasion resistance Example(cycles) No. PPD-T (%) Nylon (%) Untreated Treated C. Ex. 13 100 0 8601395 Ex. 14 90 10 1000 1850 Ex. 15 80 20 1219 2960 Ex. 16 70 30 11732122 Ex. 17 60 40 1355 1676

[0044] These Examples demonstrated the unexpected increase in abrasionresistance when the fabrics of Examples 14-17 were heat treated.Further, the Examples 14-17 demonstrated an unexpected increase inabrasion resistance of fabrics made with yarns that were blends of PPD-Tand nylon compared to fabrics made from yarns of PPD-T alone.

What is claimed is:
 1. A yarn having improved abrasion resistancecomprising (a) aramid fibers and (b) up to 40 weight percent of fibersof synthetic polymers having a melting point between 200 and 300 degreesC., based on the relative amounts of components (a) and (b) only, saidyarn having been heat treated at a temperature below the melting pointof the fibers of component (b).
 2. The yarn of claim 1, wherein thefibers of component (a) are fibers of para-aramid.
 3. The yarn of claim1, wherein the fibers of component (a) are fibers of p-phenyleneterephthalamide.
 4. The yarn of claim 1, wherein the fibers of component(b) are fibers of nylon, polyester, or blends thereof.
 5. The yarn ofclaim 1, wherein the fibers of component (b) are present in an amount offrom 5 to 30 weight percent based upon the total weight of the fibers ofcomponents (a) and (b) only.
 6. The yarn of claim 1, wherein the fibersof component (b) are present in an amount of from 10 to 25 weightpercent based upon the total weight of the fibers of components (a) and(b) only.
 7. The yarn of claim 1, wherein the fibers are staple fibershaving lengths from 2.5 to 15 centimeters.
 8. The yarn of claim 1,wherein the fibers of component (b) are fibers of nylon and the yarn isheat treated at a temperature up to about 250 degrees C.
 9. The yarn ofclaim 1, wherein the fibers of component (b) are fibers of polyester andthe yarn is heat treated at a temperature up to about 250 degrees C. 10.The yarn of claim 1, wherein the yarn is heat treated for an amount oftime up to about 20 minutes.
 11. A fabric having improved abrasionresistance comprising (a) aramid fibers and (b) up to 40 weight percentof fibers of synthetic polymers having a melting point between 200 and300 degrees C., based on the relative amounts of components (a) and (b)only, said fabric having been heat treated at a temperature below themelting point of the fibers of component (b).
 12. The fabric of claim11, wherein the fibers of component (a) are fibers of para-aramid. 13.The fabric of claim 11, wherein the fibers of component (a) are fibersof p-phenylene terephthalamide.
 14. The fabric of claim 11, wherein thefibers of component (b) are fibers of nylon, polyester, or blendsthereof.
 15. The fabric of claim 11, wherein the fibers of component (b)are present in an amount of from 5 to 30 weight percent based upon thetotal weight of the fibers of components (a) and (b) only.
 16. Thefabric of claim 11, wherein the fibers of component (b) are present inan amount of from 10 to 25 weight percent based upon the total weight ofthe fibers of components (a) and (b) only.
 17. The fabric of claim 11,wherein the fibers are staple fibers having lengths from 2.5 to 15centimeters.
 18. The fabric of claim 11, wherein the fibers of component(b) are fibers of nylon and the fabric is heat treated at a temperatureup to about 250 degrees C.
 19. The fabric of claim 11, wherein thefibers of component (b) are fibers of polyester and the fabric is heattreated at a temperature up to about 250 degrees C.
 20. The fabric ofclaim 11, wherein the yarn is heat treated for an amount of time up toabout 20 minutes.
 21. The fabric of claim 11, wherein the fabric iswoven.
 22. The fabric of claim 11, wherein the fabric is knitted.
 23. Anarticle made from the yarn of claim
 1. 24. An article made from thefabric of claim
 11. 25. A process for preparing an abrasion-resistantyarn comprising the steps of providing a yarn comprising (a) aramidfibers and (b) up to 40 weight percent of fibers of synthetic polymershaving a melting point between 200 and 300 degrees C., based on therelative amounts of components (a) and (b) only, and heat treating theyarn at a temperature below the melting point of the fibers of component(b).
 26. The process of claim 25, further comprising the steps of heattreating the yarn for 20 minutes or less.
 27. A process for preparing anabrasion-resistant fabric comprising the steps of providing a fabriccomprising (a) aramid fibers and (b) up to 40 weight percent of fibersof synthetic polymers having a melting point between 200 and 300 degreesC., based on the relative amounts of components (a) and (b) only, andheat treating the fabric at a temperature below the melting point of thefibers of component (b).
 28. The process of claim 27, further comprisingthe steps of heat treating the fabric for 20 minutes or less.